void main() {
    Teacher teacher1 = new Teacher("T001", "张老师", "男");
    Teacher teacher2 = new Teacher("T002", "李老师", "女");
    Course course1 = new Course("C001", "Java编程", "A101", "周一 8:00-10:00", teacher1);
    Course course2 = new Course("C002", "数据结构", "B202", "周三 14:00-16:00", teacher2);
    teacher1.setCourse(course1);
    teacher2.setCourse(course2);
    IO.println(teacher1.displayInfo());
    IO.println(teacher2.displayInfo());
    IO.println();
    Student student1 = new Student("S001", "小明");
    Student student2 = new Student("S002", "小红");
    student1.selectCourse(course1);
    student1.selectCourse(course2);
    student2.selectCourse(course1);
    IO.println();
    student1.printTimetable();
    IO.println();
    student2.printTimetable();
    IO.println();
    student1.dropCourse(course2);
    IO.println();
    student1.printTimetable();
}
